The reason this message appears is that Office 365 files are not supported by Ephorus in today's version.

Use one of the following workarounds:

Workaround 1: Save the file to your PC.
Open it and make a change. It is enough to click 'Save As' and save the document locally on your PC.
Resubmit the document in the submission task in itslearning.

Workaround 2: Create documents in Word Online, rather than directly in OneDrive.
To do this, open Word Online and click File > New.
Back in OneDrive, download document.
This document can be uploaded in a submission task in itslearning. You do not have to open and save again.